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Reading Barcodes from an Image - III

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4.87 (119 votes)
19 Oct 2009CPOL
Detects Code39, EAN, and Code128 barcodes in an image.

Screenshot

Acknowledgement

This project is based on the CodeProject article: Reading Barcodes from an Image - II by qlipoth. I asked and got permission from qlipoth to publish an enhanced version of his code.

Introduction

My company has a need for reading barcodes from images that also contain text on the same page as the barcode(s). When searching for a solution in C#, I found qlipoth's CodeProject article: Reading Barcodes from an Image - II. His code came a long way towards what I wanted, but I needed a few improvements. In the end, my changes amounted to a significant rewrite that justifies a new CodeProject publication.

Background

This code has several improvements compared to the original code written in 2005:

  1. Validation is added for Code39 barcodes. The code has much less chance of detecting a "barcode" that is not actually present.
  2. Detection speed is improved. The main problem in the original project was that it used Bitmap.RotateFlip, and that function is quite slow.
  3. Added EAN/UPC and Code128 barcode support. The original project could only detect Code39 barcodes.
  4. Fixed some bugs that were reported for qlipoth's project and for the related project Reading Barcodes from an Image published by Benjamin Liedblad in 2004.

Using the code

To open the solution, you'll need Visual Studio 2008. However, I have not used any constructs that are not .NET 1.1 compatible, so the actual code should also be compilable in Visual Studio 2003 or 2005.

To use the code, call FullScanPage or ScanPage with the Windows Bitmap object containing your image. The included TestApp (written in VB.NET) demonstrates the basic use:

Dim barcodes As New System.Collections.ArrayList
BarcodeImaging.FullScanPage(barcodes, Me.PictureBox1.Image, 100)
If barcodes.Count > 0 Then
  ' Found one or more barcodes ...

The numscans parameter in both functions indicates how many bands of pixels should be scanned across or down the image. With a higher number, the code finds more barcodes, but of course, will also run slightly slower. Usually 50 - 100 scans will be OK to find all barcodes on a full page image.

Difference between FullScanPage and ScanPage

FullScanPage always scans horizontally and vertically, and attempts to detect all supported barcode types. If you know that your input material is always scanned in the same orientation, or if you do not need detection of all barcode types, you can make your program run faster by using ScanPage.

public static void ScanPage(ref System.Collections.ArrayList CodesRead, 
       Bitmap bmp, int numscans, ScanDirection direction, BarcodeType types)

With the additional parameters direction and types, you can fine-tune barcode detection:

  • direction: can be ScanDirection.Vertical or ScanDirection.Horizontal. Use Vertical for detecting barcodes with vertical bars, or Horizontal if you expect barcodes that are rotated 90 degrees.
  • types: Pass BarcodeType.All to detect all supported barcode types, or you can specify one or more specific barcode types, like this:
    ScanPage(ref CodesRead, bmp, numscans, ScanDirection.Vertical,
             BarcodeType.Code39 | BarcodeType.Code128);

    Supported types are Code39, EAN, and Code128. The EAN reader will also detect UPC codes.

Points of interest

  • The EAN reader also reads the 2 or 5 digits supplemental barcodes often found on books and periodicals. As shown in the screenshot, a supplemental barcode will be returned as a separate barcode string starting with "S".
  • The Code128 reader has mixed code page support. The serial number in the sample image Code128test-CodeC.png starts as Code C, but the last digit is added as Code B.
  • The code uses a more advanced approach for measuring the "narrow bar width" than qlipoth's and Liedblad's versions. This should allow for better detection rates when reading EAN and Code128. In Code39, we only need to distinguish between narrow and wide bars, but the other barcode types use four different bar widths.
  • I have added the concept of "barcode zones", to allow detection of differently scaled barcodes on the same scan line. In Code128test-CodeC.png, this enables the software to read both the serial number and the UPC code that are printed side-by-side.

    barcode zones

References

I used the following references while writing this project:

  1. For implementing EAN detection: Wikipedia articles on the European Article Number, EAN-2, and EAN-5.
  2. For implementing Code 128: the character table and checksum calculation as published on code128barcodes.com, and the barcode generator published by IDAutomation.com Inc., for testing.

History

  • October 5, 2009: Original.
  • October 19, 2009: Improved Code39 detection, bugfixes. Added VB.NET translation of the barcode detection class and the COM interface provided by Alessandro Gubbiotti.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Berend Engelbrecht
Software Developer (Senior) Decos Software Engineering BV
Netherlands Netherlands
No Biography provided

Comments and Discussions

 
GeneralRe: Miles Behind Pin
hground24-Nov-09 3:28
memberhground24-Nov-09 3:28 
GeneralRe: Miles Behind Pin
tonym00127-Nov-09 10:58
membertonym00127-Nov-09 10:58 
AnswerRe: Miles Behind Pin
Berend Engelbrecht27-Nov-09 23:05
memberBerend Engelbrecht27-Nov-09 23:05 
GeneralRe: Miles Behind Pin
tonym0014-Dec-09 13:50
membertonym0014-Dec-09 13:50 
GeneralReading Barcodes : some doubt ... Pin
beguroto2-Nov-09 22:17
memberbeguroto2-Nov-09 22:17 
GeneralRe: Reading Barcodes : some doubt ... Pin
Berend Engelbrecht3-Nov-09 6:26
memberBerend Engelbrecht3-Nov-09 6:26 
GeneralBar widths Pin
supercat928-Oct-09 12:22
membersupercat928-Oct-09 12:22 
GeneralRe: Bar widths Pin
Berend Engelbrecht28-Oct-09 13:03
memberBerend Engelbrecht28-Oct-09 13:03 
Dear supercat9,

For any computing problem there are any number of solutions and you are of course welcome to publish your own. If you can improve on mine, you are welcome too - that is what I did with qlipoth's work and he with Liedblad's original version before me.

However, I have the feeling that you are trying to solve a problem that is already sufficiently solved (the published code already detects Code39, Code128 and EAN, also in bad quality scans), while not progressing in the problem that is still open: my code is not able to detect rotated barcodes very well, if at all. I tried a basic Hough transform and it works well only if the rectangle where the barcode is located is already known, so that the transform can be applied on an area without other image elements. My application however needs to detect multiple barcodes on pages that also have text and other graphics. Just applying a Hough transform over the full page often badly malfunctions.

If you look at this image, you may also notice a problem with the bar counting that you propose: actually in a rotated barcode, the scan line will not cover the full barcode and thus not return a complete bar count. What I plan to do is find partial barcodes (with the same approach that I use now) and if I find one, use that information to identify the rotated rectangle containing the barcode fragment that was found.

One more problem that you should be aware of: you cannot expect a 2:1 wide/narrow bar ratio. I have seen both 1.7 : 1 and 4:1 in Code 39. Also, in a bad scan the white bars are drawn too wide and the black bars too narrow (or the other way around), because the lighting is off. This causes a wide white bar to have a very different size from a wide black bar. This is the reason why the current version of the code does measurements for white and black bars separately. I had to later relax the constraints that I set on the ratio between white and black, to be able to pass more of our test material.

Finally, the reason why the code averages several rows of scan lines vertically is to compensate for noise. The image usually has white pixels in the middle of a black bar and black pixels in the background, and that will screw bar width calculations and bar counts if you consider just one scan line at the time. Unfortunately, the averaging technique is also a prime reason why the code is so sensitive for rotation: if you average two rotated bars vertically, the gap between them will be grayed out in the average scan line. I have tried to disable the averaging in good quality skewed scans and in that case detection actually improves. However, our customers manage to produce much more bad than good quality imaging, so the overall detection rate over our test set went down Frown | :(

Here is a sample of what I am up against: fail1a.tif. The current version of the code can just detect this barcode (with a bit of luck). Please zoom in on the image and notice in how bad shape the bars are ...

Best regards,

Berend
QuestionPossible to integrate scew angle? Pin
infal23-Oct-09 4:14
memberinfal23-Oct-09 4:14 
AnswerRe: Possible to integrate scew angle? Pin
Berend Engelbrecht23-Oct-09 22:25
memberBerend Engelbrecht23-Oct-09 22:25 
GeneralRe: Possible to integrate scew angle? Pin
infal24-Oct-09 6:54
memberinfal24-Oct-09 6:54 
GeneralRe: Possible to integrate scew angle? [Modified: proposed strategy for detecting skewed/rotated barcodes] Pin
Berend Engelbrecht24-Oct-09 7:05
memberBerend Engelbrecht24-Oct-09 7:05 
GeneralThank you Pin
babakzawari23-Oct-09 3:11
memberbabakzawari23-Oct-09 3:11 
QuestionSupport for rotaded, skewed low resoluted images? Pin
infal22-Oct-09 23:15
memberinfal22-Oct-09 23:15 
AnswerRe: Support for rotaded, skewed low resoluted images? Pin
Berend Engelbrecht22-Oct-09 23:30
memberBerend Engelbrecht22-Oct-09 23:30 
GeneralTIFF support Pin
ndisampson22-Oct-09 18:40
memberndisampson22-Oct-09 18:40 
GeneralRe: TIFF support [modified] Pin
Berend Engelbrecht22-Oct-09 19:18
memberBerend Engelbrecht22-Oct-09 19:18 
GeneralCool but does not allways work... PinPopular
infal22-Oct-09 2:25
memberinfal22-Oct-09 2:25 
GeneralRe: Cool but does not allways work... Pin
Berend Engelbrecht22-Oct-09 2:31
memberBerend Engelbrecht22-Oct-09 2:31 
GeneralRe: Cool but does not allways work... [modified] Pin
infal22-Oct-09 6:36
memberinfal22-Oct-09 6:36 
GeneralCause of problem and bugfix Pin
Berend Engelbrecht22-Oct-09 8:45
memberBerend Engelbrecht22-Oct-09 8:45 
GeneralRe: Cause of problem and bugfix Pin
infal22-Oct-09 23:16
memberinfal22-Oct-09 23:16 
GeneralRe: Cause of problem and bugfix Pin
hairy_hats28-Mar-11 1:44
memberhairy_hats28-Mar-11 1:44 
GeneralLooks really cool! Pin
Shane Story7-Oct-09 3:07
memberShane Story7-Oct-09 3:07 
JokeToday Google made a homepage just for me Pin
Berend Engelbrecht6-Oct-09 21:41
memberBerend Engelbrecht6-Oct-09 21:41 

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Article
Posted 5 Oct 2009

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